This invention relates to an opening mechanism for an intravascular shunt defect closure device such as described in U.S. Pat. No. 3,874,388. As explained in the patent, abnormal openings, holes, or shunts can occur between the chambers of the heart or the great vessels (interatrial and interventricular septal defects or patent ductus arteriosus and aorthico-pulmonary window respectively), causing shunting of blood through the opening. The deformity is usually congenital, resulting from a failure of completion of the formation of the septum, or wall, between the two sides during fetal life when the heart forms from a folded tube into a four-chambered, two unit system.
The patent describes a device and method for closing such defects without open-heart surgery. The devices described in the patent are similar to an umbrella and include a central hub and a plurality of struts which are pivotally mounted on the hub. A disc of sheet material such as Dacron or the like is attached to the struts, and the struts are pivotable from a collapsed or closed position in which the struts extend generally parallel to the axis of the hub to an expanded or open position in which the struts extend generally perpendicularly to the axis of the hub. When the struts are in the open position, the Dacron disc is maintained generally flat and is moved into position to close the shunt.
The patent describes shunt closure devices for closing an atrial septal defect (ASD), a ventricular septal defect (VSD), and a patent ductus arteriosus (PDA). In each case the umbrella-like closure device is located in position to close the defect by inserting a catheter which carries the collapsed device into the heart. The device is then pushed out of the catheter and caused to expand by opposing forces exerted on the device by an inner catheter and, in the case of a left atrial or ventricular defect, an obturator wire or, in the case of a right atrial or ventricular defect, retraction ties or elevating struts.